Los Angeles, the second most populous city in the U.S., has made history by becoming the first major city to require all new and refurbished homes have a "cool roof." On December 17, 2013 the Los Angeles City Council unanimously passed an update to its Municipal Building Code. A cool roof is one that "reflects and emits the sun's heat back to the sky instead of transferring it to the building below," according to the Cool Roof Rating Council.

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Cool roofs are great in an area like Los Angeles which has warm summers and mild winters. A white roof is one of the most popular choices for a cool roof, and the Lawrence Berkeley National Laboratory's Heat Island Group estimates that a white roof can reflect 80 percent of sunlight in the summer, making the building cooler. A cooler building in the summer means less air conditioning is used and that saves homeowners money. Cool roofs offer other benefits, according to both Climate Resolve, which worked on the ordinance with the City Council, and the Cool Roof Rating Council. Those other benefits include improving air quality by reducing the formation of ozone, reducing greenhouse gas emissions, and decrease roof maintenance costs.